A Hill-Climbing Optimization Approach for Closed-Loop Auto-Tuning of the Grid-Connected Ripple-Port Inverters

Single phase grid-tied inverters have a characteristic double frequency power ripple. Such double frequency ripple could negatively impact the maximum power point tracking capability of the converter and dropping the overall energy harvest from the photovoltaic (PV) energy resource. Classically, a bulk capacitor is used at the dc bus to filter out this double frequency power ripple, but this ends up being large due to the low frequency and large energy stored. An active filtering technique such as the ripple port inverter has shown very effective reduction in the capacitor size required at the dc link to filter out the double frequency ripple. This paper provides a mathematical formulation of the different factors that affect the ripple port inverter, so it can be tuned for maximum double frequency rejection. It also provides a closed-loop framework based on the hill-climbing optimization technique to automatically tune the ripple port inverter to minimize de link double frequency ripple.